The present invention relates to an apparatus for aligning with each other the webs to be glued together while they are running for the production of corrugated fiberboards.
In a corrugating machine for producing corrugated fiberboards, a medium liner from a mill roll stand is fed to a single facer where it is corrugated, and a linerboard from another mill roll stand is glued to one side of the corrugated liner to produce a single faced corrugated fiberboard, which is fed with another linerboard to a double facer where the latter is glued to the other side of the single faced corrugated fiberboard to produce a double faced corrugated fiberboard. Also, in order to produce a double wall corrugated fiberboard, two single faced corrugated fiberboards and a linerboard are glued together.
The double faced or double wall corrugated fiberboard thus formed is trimmed to remove any excess selvage portions to produce final products. In the production of these fiberboards, automatic aligning of the two or more webs to be glued together with one another is very important to minimize the production of defective articles and to save labor.
Conventional web alignment devices are provided at a position close to the web gluing station, e.g. somewhere between a preheater and the double facer. Since at such a position a considerably large tension is applied to the webs by a tension unit to keep them from running out of true, correction of displacement at such a position frequently causes breakage of the webs.
Another shortcoming of conventional web alignment devices is that the time required for a web displacement detector to follow a lateral displacement of the web is not taken into consideration. The following-up time required is particularly large after splicing or after a change of the web width. After splicing, the web is liable to run out of true and takes a considerable time to come back to a stable running condition. Such a fact was not taken into account.